An ADC has been widely used in various fields, and for example, has come to be built in battery-powered portable electronic equipment, a micro controller unit (MCU) that is used for various electronic devices, and the like. Therefore, it is desirable that the power consumption and the footprint of the ADC are reduced.
In the related art, for example, as an ADC with low-power consumption, a successive approximation register (SAR) ADC using a capacitor digital/analog converter (capacitor DAC) is known.
Such an SAR ADC includes the capacitor DAC, a comparator, and a control logic circuit (SAR logic circuit), and improves the resolution by repeating comparison processing by the comparator several times.
In addition, in the related art, for example, a pipelined ADC has been proposed in which a plurality of AD conversion units are connected to each other in multi-stages and executes a pipeline operation, so that the number of comparators is reduced while the operation speed is maintained.
In addition, recently, a pipelined SAR ADC has been also proposed in order to improve the power consumption and the processing speed in the pipelined ADC.
In the related art, various ADCs have been proposed such as the pipelined SAR ADC and an SAR ADC in which capacitor mismatch of a used capacitor DAC (switched capacitor circuit) is reduced.
C. P. Hurrell et al., “An 18 b 12.5 MS/s ADC With 93 dB SNR,” IEEE Journal of Solid-State Circuits, vol. 45, No. 12, December 2010, M. Furuta et al., “A 10-bit, 40-MS/s, 1.21 mW Pipelined SAR ADC Using Single-Ended 1.5-bit/cycle Conversion Technique,” IEEE Journal of Solid-State Circuits, vol. 46, No. 6, June 2011, and Y. Chen et al., “Split Capacitor DAC Mismatch Calibration in Successive Approximation ADC,” IEEE 2009 Custom Integrated Circuits Conference (CICC), pp. 279-282, September 2009 are the related arts.
In the related art, there has been proposed that the pipelined SAR ADC that includes the AD conversion units in multi-stages, and an amplifier is provided between the stages of the AD conversion units that execute the pipeline processing.
The amplifier (residue amplifier) that is provided between the stages receives, as an input, the remaining analog signal (residual voltage) of an analog signal on which digital conversion has been performed by a certain bit portion in the previous AD conversion unit, amplifies the residual voltage, and outputs the amplified voltage to the latter AD conversion unit.
However, there is a problem, for example, in the ADC that is built in battery-powered portable electronic equipment, an MCU, and the like because the residue amplifier that is provided between the stages causes an increase in the power consumption and the footprint.